Habit forming in humans is reflexive. We change ourselves and our environment in order to attain maximum comfort and well being. It is the effort that goes into these adaptive processes that forms a habit. The habit is intended to prevent us from constant experimenting and risk taking. The greater our well being, the better we function and the longer we survive.
Actually, when we get used to something or to someone â we get used to ourselves. In the object of the habit we see a part of our history, all the time and effort we had put into it. It is an encapsulated version of our acts, intentions, emotions and reactions. It is a mirror reflecting that part in us which formed the habit in the first place. Hence, the feeling of comfort: we really feel comfortable with our own selves through the agency of our habitual objects.
Because of this, we tend to confuse habits with identity. When asked WHO they are, most people resort to communicating their habits. They describe their work, their loved ones, their pets, their hobbies, or their material possessions. Yet, surely, all of these do not constitute identity! Removing them does not change it. They are habits and they make people comfortable and relaxed. But they are not part of one's identity in the truest, deepest sense.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)